TUKWILA — Sounders FC practice had some unexpected visitors Saturday, the day before the decisive second leg of the Western Conference finals.

Several full-voiced fans, with flags in hand, braved the wind and rain at the team’s training facility and brought a large banner.

The message: “We beat ‘em before. We’ll beat ‘em again!”

It was a last bit of encouragement before an attempt at a monumental comeback. Seattle is behind, 3-0, to the defending champion Los Angeles Galaxy in the aggregate-goals series heading into Sunday’s 6 p.m. finale at CenturyLink Field.

The Sounders need a four-goal win to advance to MLS Cup. A three-goal win sends the series to a 30-minute overtime with a penalty-kick tiebreaker if a winner still isn’t determined. Anything less means Seattle’s season is over.

“The bottom line is we know the situation — we are playing at home and fighting for our lives,” said midfielder Brad Evans. “There is no other way to put it: It’s do-or-die time.”

So is Sunday’s an impossible task? Not quite, but just about.

Goalkeeper Michael Gspurning called upon a saying in his native Austria that describes the situation.

“We don’t have a chance, but we want to use it,” he said, hoping the subtext of the phrase comes through after his translation.

Coach Sigi Schmid put it another way: “We just need to have a historic moment.”

The Sounders will look to get any advantage they can against the Galaxy. Some have hoped for rain in the forecast, which, combined with slick artificial turf, could make matters difficult for the visitors from Southern California.

And on the mental side?

“We could do all kinds of motivational things right now,” Schmid said. “You could talk about that, but I think it’s most important to deal with reality. Reality is we’ve dug a hole for ourselves, and all of them can look at challenges that they’ve had in their lives when they’ve overcome things and succeeded at things when probably nobody gave them a chance.

“I don’t think (Jeff) Parke thought he was going to have a 10-year career when he was the last player drafted. I don’t think Brad Evans, when he was at UC Irvine, thought he was going to play in the under-20 world championships. But those things happen. I don’t think Steve Zakuani a year and a half ago was thinking he was going to play in a conference final, possibly. They’ve overcome things. They can all point to things in the past… but it doesn’t matter what we talk about. It’s what we do on Sunday.”

Notes

• The roles of midfielder Mauro Rosales and defender Leo Gonzalez, who are each recovering from hamstring strains, will be determined at game time, Schmid said.

• Midfielders Landon Donovan (hamstring tightness) and Juninho (Achilles inflammation) are the Galaxy’s main injury concerns. Both are listed as questionable.

• More than 43,000 tickets have been sold for Sunday’s game, according to a team spokesman.